WASHINGTON — The U.S. Marine Corps is investigating allegations an unspecified number of military personnel and veterans allegedly distributed nude photos of female colleagues and other women as part of a perverse social media network that promotes sexual violence.

The explosive revelation was first reported by The War Horse and published Saturday via Reveal, part of the Center for Investigative Reporting. Potentially hundreds of Marines may be caught up in the scandal, which has shaken top Pentagon officials and prompted death threats against the Marine veteran who disclosed it. An undetermined number of nude photos were shared online by way of a Facebook group titled Marines United, according to the report. The community has nearly 30,000 members, mostly comprising active-duty U.S. Marines, Marine Corps veterans and British Royal Marines.

The unseemly episode is deeply embarrassing for the Marine Corps and the Defense Department, proud institutions that, like many college campuses around the country, have struggled to curtail widespread problems with sexual assault. At the same time, it exposes an unsettling rift within a segment of American society consistently regarded as reputable, honorable and trustworthy.

A Marine Corps spokesman at the Pentagon confirmed that an investigation is underway, telling Marine Corps Times on Saturday night that military officials are uncertain how many personnel may be involved. The spokesman, Maj. Clark Carpenter, referred additional questions to the Naval Criminal Investigative Service, but that agency's spokesman was not immediately available.

The Marines' top general, Commandant Robert Neller, declined to comment specifically about the investigation, but he condemned the behavior that's been alleged. "The success of every Marine, every team, every unit and command throughout our Corps is based on mutual trust and respect," Neller said in a statement provided to Marine Corps Times. "I expect every Marine to demonstrate the highest integrity and loyalty to fellow Marines at all times, on duty, off-duty and online."

Marine Corps Times has been unable to reach the administrator of Marines United. Defenders of the private group, following Marine Corps Times' initial report, pointed out members have helped Marines suffering from post-traumatic stress, and that the group has reacted in force to help suicidal service members.

Senior Marine Corps officials are circulating a 10-page document outlining the allegations and approved talking points about the service's effort to investigate them. Marine Corps Times obtained a copy early Sunday.